The present invention relates generally to memory cards, and more particularly to a memory card (e.g., a multi-media card or secure digital card) which is manufactured to include an internal reinforcement structure adapted to provide increased mechanical strength to resist bending and twisting under a predetermined load, thus enhancing the durability of the memory card.
As is well known in the electronics industry, memory cards are being used in increasing numbers to provide memory storage and other electronic functions for devices such as digital cameras, MP3 players, cellular phones, and personal digital assistants. In this regard, memory cards are provided in various formats, including multi-media cards and secure digital cards.
Typically, memory cards include a module which itself comprises a printed circuit board (PCB) having a conductive wiring pattern disposed thereon. Attached to one side or surface of the PCB and electrically connected to the conductive pattern thereof is a plurality of electronic circuit devices, such as semiconductor packages, semiconductor dies, and/or passive elements. In most memory cards, these electronic circuit devices and a portion of the PCB are covered or encapsulated by an encapsulant material. The PCB also includes a plurality of input/output (I/O) pads disposed on the side or surface thereof opposite that having the electronic circuit devices thereon. These I/O pads are not covered by the encapsulant material, and thus are exposed in the completed module. Attached to the module is a skin or case of the memory card, such case generally defining the outer appearance of the memory card. The module is coupled to the case such that the I/O pads disposed on the PCB are not covered by the case, and thus remain exposed in the fully assembled memory card. These I/O pads of the memory card provide an external interface for an insertion point or socket. The completed memory card has a generally rectangular configuration, with most memory cards including a chamfer formed at one edge thereof which is adjacent to the I/O pads.
Memory cards as currently known can generally be sorted into two types based on the method used to mount the electronic circuit devices to the PCB during the fabrication of the memory card. The common categories include a surface mount technology (SMT) type memory card and a chip on board (COB) type memory card. In an SMT memory card, a semiconductor package (i.e., a semiconductor die which is already encapsulated in a package body of a hardened encapsulant material) is mounted and electrically connected to the PCB, and thereafter covered with the encapsulant material to form the above-described module. In a COB memory card, a semiconductor die is mounted and electrically connected to the PCB, and thereafter covered with the encapsulant material to form the above-described module. In the case of the COB memory card, the covering of the semiconductor die with the encapsulant material serves the dual purposes protecting the die and increasing the overall strength of the memory card. In the case of the SMT memory card, the covering of the semiconductor package with the encapsulant material is not primarily for the purpose of protecting the semiconductor package (which already includes a package body of a hardened encapsulant material), but rather for the purpose of increasing the overall strength of the memory card. Even in the COB memory card, the primary protection for the internal semiconductor die is provided by the case. Thus, in SMT memory cards and to a large extent in COB memory cards, the covering of the electronic circuit devices with the encapsulant material is for purposes of increasing the mechanical strength of the memory card, and not primarily for purposes of protecting such electronic circuit devices. As will be recognized, the added mechanical strength imparted to the memory card as a result of the inclusion of the hardened encapsulant material underneath the case makes the memory card less susceptible to bending or twisting under a predetermined load, thus allowing it to pass various mandated bending and twisting tests under predetermined conditions.
However, with particular regard to the SMT memory card wherein the encapsulant material is used only to impart increased mechanical strength to the memory card, the need to include the additional encapsulation step increases the number of manufacturing processes and hence the manufacturing cost for such memory card. Further, the need to include the encapsulant material under the case reduces the effective interior space in the memory card, which is undesirable due to the constant need for memory cards of increased capacity. The present invention addresses and overcomes these drawbacks by providing a memory card construction wherein a case of the memory card is provided with an internal reinforcement structure which effectively eliminates the need for an underlying layer of encapsulant material. These as well as other features and advantages of the present invention will be described in more detail below.